Piston operated circuit breaker



Feb. 23, 1965 R. N. *YECKLEY EI'AL PISTON OPERATED CIRCUIT BREAKER 2 Sheets-Sheer. 1

Filed Nov. 14, 1960 ACCUMULATOR COMPRESSOR FILTER Feb. 23, 1965 yz'c ETAL 3,171,000

PISTON OPERATED CIRCUIT BREAKER Filed NOV. 14, 1960 2 Sheets-Shae t 2 United States Patent Pa., assignors to Westinghouse Electric Corporation,

East Pittsburgh, Pa., a corporation of Pennsylvania Filed Nov. 14, 1960, Ser. No. 69,081 13 Claims. (Cl. 200-82) This invention relates to electric circuit breakers and more particularly to circuit breakers actuated by hydraulic mechanisms.

Circuit breakers having hydraulic actuating mechanisms for both closing and opening the breakers have not been used extensively in the past because of the difficulty of achieving high speed opening of the breakers by hydraulic means. I

Accordingly, an object of the invention is to provide a circuit breaker having a hydraulic actuating mechanism which effects high speed opening of the breaker.

Another object of the invention is to provide a hydraulic actuating mechanism with means for rapidly dumping high-pressure fluid from one side of a piston to effect high speed opening operation of a circuit breaker.

A further object of the invention is to provide an improved compactly constructed hydraulic operating mechanism.

A still further object of the invention is to provide an improved hydraulic operating mechanism constructed with a minimum number of hydraulic conduits in the system.

A further object of the invention is to provide a circuit breaker hydraulic actuating mechanism having three valves connected in series relationship and operable to effect both opening and closing of the circuit breaker.

Another object of the invention is to provide a circuit breaker with a hydraulic actuating mechanism having valve means constructed to permit latching of the circuit breaker in one position by means of a light-load latch.

In circuit breakers operated by means of hydraulic operating mechanisms, it has often been a problem to align the piston rod, which is rigidly connected to the piston, with the operating rod of the circuit breaker.

Accordingly, another object of the invention is to pro vide a hydraulically operated circuit breaker wherein the piston and piston rod are constructed in such a manner that alignment of the piston rod with the circuit breaker operating rod is not a critical problem.

Other objects of the invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of the invention, a circuit breaker is provided with a hydraulic operating mechanism that includes a cylinder and a piston movable within the cylinder to actuate the circuit breaker operating rod. A sump is connected directly to a plate that serves as one end wall of the hydraulic cylinder. A

main valve is disposed within the sump and is connected directly to the end-wall plate so that, upon operation of the main valve; the hydraulic fluid can be'rapidly dumped from one side of the piston through the main valve into the sump. Other than the main valve, there are no hydraulic lines between the cylinder and sump through which the dumped fluid must pass. A control valve for operating the main valve is connected directly to the sump,

and a pilot valve that is connected directly to the control valve operates the control valve. Electromagnetic means are provided for operating the pilot valve to effect both opening and closing of the circuit breaker. A light-load latch is provided for maintaining the pilot valve in one of its two operating positions, which valve is biased to the other operating position by spring means.

The piston rod is connected to the piston by means of a connection that permits a wobbling or swiveling 3,171,000 Patented Feb. 23, g 1965 movement of the piston rod about its longitudinal axis ,'so that alignment of the piston rod with the circuit breaker operating rod is not a critical problem. The piston rod is disposed within a tube that is rigidly connected to the piston and which reciprocates linearly with are! piston and piston rod to seal the opening in the cylinder end wall through which the piston rod and tube pass.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a diagrammatic view of a circuit breaker embodying the principles of the invention;

FIG. 2 is an enlarged view, partly in section, illustrating part of the hydraulic operating mechanism;

FIG. 3 is a further enlarged view, partly in section, illustrating the pilot valve and pilot valve operating means; and

FIG. 4 is a side elevational view, partly in section, of theclosing electromagnet.

Referring to FIG. 1 of the drawings, a circuit breaker 3 is shown therein comprising a circuit breaker operating rod 5 having secured thereto, at one end, a'movable contact structure 7 for controlling three phases of a power distribution system. The other end of the operating rod 5 is connected at 9 to a piston rod that is actuated by a hydraulic operating mechanism indicated generallyat 11 The hydraulic operating mechanism 11 includes a main part l3, to which is connected a sump 14, a filter 17, a compressor 19, and an acumulator 21.

Referring now to FIG. 2, the main part 13 of the hydraulic mechanism 11 (FIG. 1) includes a supporting plate 23 which supports the mechanism 13 and also functions as an end wall of a cylinder 25. A second plate 2.7, having an opening thereinthrough which the cylinder 25 extends, is welded to the cylinder 25 and is fastened to the plate 23 by means of bolts (not shown) to support the cylinder 25 in position. Another cylinder 29 having less height and less diameter than the cylinder 25, is secured within the upper portion of the cylinder 25, and serves as a bumper for limiting upwardmovement of a movable piston structure indicated generally at 31.

The movable piston structure 31 includes a main piston piston 33 to prevent upward movement of the piston rod 39 relative to the piston 33. The support member 4l is threadedly secured into the lower portion of the piston 33 and it has a concave surface 49 that mates with'a convert surface Slat the lower end of the piston rod 39 to prevent downward movement of the piston rod 39 relative to the piston 33. The piston rod 39 is heldin 'pasitien only by the means of the engagement of the convex surface 45 of the support member 43 with the concave surface47 of I piston 33, and the engagement of the concave'sui'face 49 of the support member 41 with the convex surface 51 of the piston rod 39 which engagements provide a ball-and:

socket or universal type connection permitting a wobbling or swiveling motion of the rod 39 relative 'to the piston 33.

A flanged sealing member 53 is plugged into the openi g in the plate 23 for receiving the tubular member 37. The

member 53 is provided with two inner O-ring seal members 1 57 and an outer O-ring type seal member 59 to seal off the opening in the plate 23. As seen in FIG. 2, the sealat ing plug 53 is attached to the plate 23 by means of two bolts 61.

The piston rod 39, which is operated to both open and close the breaker, is connected to the circuit breaker operating rod (FIGS. 1 and 2) in any suitable manner. As was hereinbefore described, the connection between the piston 33 and the piston rod 339 permits a wobbling or swiveling motion of the piston rod 39 with respect to the piston 33, thereby allowing operative connection of the piston rod 39 with the breaker rod 5 even when these parts are not in perfect alignment. Although the piston rod 39 wobbles or swivels with respect to the cylinder 25, the opening provided in the plate 23 for the piston rod 39 is effectively sealed by means of the tubular sealing member 37, that is rigidly secured to the piston 33 to reciprocate with the piston, and by means of the sealing member 53 that cooperates with the sealing member 37 to provide an effective seal.

A conduit 65 is bolted to a tubular support member 67 that is welded or otherwise attached to the cylinder 25. Fluid under pressure from the compressor 19 (FIG. 1) and accumulator 21, is supplied to the upper side of the piston 33 (FIG. 2) through the conduit 65.

A plate 69, which serves as the lower end wall of the cylinder 25, is welded or otherwise secured to the lower end of the cylinder. The sump 14 comprises a sump housing 71 that is fastened by bolts (not shown) to the lower side of the plate 69. A main valve, indicated generally at 73, is disposed within the sump 71, and is attached to the lower end of the plate 69 by means of a plurality of bolts 75, only one being shown, that pass through openings in a flange 77 of a housing 79 and are threaded into tapped openings in the plate 69. An opening 80 in the cylinder end wall 69 is continuous with an opening 81 in the upper end of the main valve housing 79 and with an opening 83 in a large poppet-type valve member 85. The valve member 85 is slidably disposed within the housing 79 and is biased to the closed position shown in FIG. 2 by means of a spring 87. A smaller check valve member 89 is provided to close off the opening 83 in the valve member 85. The check valve member 89 is biased toward its closed position (FIG. 2) by means of a spring 91 that is seated, at its upper end, against the valve member 85 and, at its lower end, on an orifice member 93 that is secured to a stem part 94 of the check valve member 89. The orifice member 93 moves within a cylinder member 95 that is rigidly secured to the inside of the housing member 79.

The valve member 85 is held in the closed position shown by means of fluid pressure on its lower side and by means of the spring 87. The check valve 89 is held in the closed position shown by means of fluid pressure on its upper side and by means of the spring 91.

Fluid under high pressure is supplied to the lower side of the piston 33 through the main valve 73. The fluid from the compressor 19 and accumulator 21 (FIG. 1) is supplied to the conduit 65 (FIG. 2), a conduit 99, a branch conduit 101, a control valve indicated generally at 103, a nozzle 105 of the main control valve housing 7 9, through the orifice member 93, and through the openings 83, 81 and 80 of the members 85, 79 and 69, respectively, which openings lead into the cylinder 25. The fluid is dumped from the lower side of the piston 33 through the openings 80 and 81 in the members 69 and 79, respectively, through a port 108, shown closed in FIG. 2, then through a conduit 109 in the side of the housing 79 and into the sump chamber 14. A conduit 111 is bolted to the sump housing providing a passage to the filter 17 (FIG. 1).

The control valve 103 includes a housing 115 which is fastened by bolts, not shown, to the lower side of the sump housing 71. A combination poppet and spool type valve 117 having a piston member 119 secured to one end thereof, is slidably mounted within the housing 115. Openings 121 are provided at the other end of the valve 117 to prevent the trapping of fluid at that end of the valve. In the position shown in FIG. 2, fluid under pressure enters the main valve 73 by passing from the high pressure branch conduit 101, through the open left side of a port 124, then through the open right side of a port 125 and into the nozzle of the main valve 73. As was previously described, this high pressure fluid then flows through the main valve 73 into the cylinder 25 to maintain the piston 33 and, hence, the contacts 7, in the closed position.

A pilot valve indicated generally at 131 (FIG. 2) is fastened by bolts, not shown, to one end of the control valve housing 115. An elongated poppet-type valve 133 (FIG. 3) is slidably disposed within the housing of the pilot valve 131. As seen in FIG. 3, fluid under pressure from the conduit 99 tends to unseat the valve member 133. This motion is prevented, however, by engagement of the upper end of the valve member 133 with a shaft structure 135 that is part of a pilot-valve operating means indicated generally at 139.

The pilot-valve openating means 139 includes an opening electromagnet 143 and a closing electromagnet 145. The opening magnet 143 includes a supporting bracket 147, a coil 148 and an armature 149 which is shown in the open position in FIGS. 2 and 3. The supporting bracket 147 is secured to a U-shaped supporting member 150 which, in turn, is fastened to a supporting plate 151 that is bolted (FIG. 2) to the plate 69. The shaft structure 135 includes a part 155 that is secured to the armature 149 and passes up through the coil 148, then up through openings in the brackets 147 and 150, and is secured at its upper end to a spring support 157. A spring 159 is supported between the upper leg of the U-shaped bracket 150 and a flange 161 of the spring support 157 and it biases the spring support 157 and the shaft structure 135 downward as seen in FIG. 3.

The closing electromagnet 145 comprises a supporting bracket 171, a coil 173 and an armature 175. A shaft member 177 passes through the coil 173, and is secured to the armature 175. The shaft 1'77 passes through an opening in brackets 178 and 179. The bracket 178 is bolted to the housing 115 of the pilot valve 131. A spring 181 is biased between a lower spring support 183 which is threaded to the shaft member 177, and the bracket 179, biasing the armature and toward the open position. Spring members 176 are provided between the bracket 179 and a spring support 178 that is attached to the shaft 177. The springs 176 serve to absorb shock during operation of the electromagnet 145. A bell-crank type latch 185 is pivotally mounted on a bracket 187 by means of a pivot pin 189. The latch 185 is attached to the upper end of the shaft 177 by means of a screw member 191 that passes through an opening in one end of the latch 185, and is threaded into the member 177. The bracket 187 is bolted (FIG. 2) to the housing 71 of the sump chamber 14.

As seen in FIG. 3, the fluid under pressure from the conduit 99 biases the valve member 133 of the pilot valve 131 in opening direction. This movement is prevented, however, by the spring 159 which biases the shaft structure 135 downward with enough force to overcome the force of the fluid pressure on the valve 133. Upon energlzation of the coil 149 of the opening electromagnet 143, the difference between the downward spring force and the upward fluid pressure force on the shaft structure 135 is overcome, and the armature 149 is thrust upward moving the shaft structure 135 upward to permit the fluid under pressure from the conduit 99 to force the valve member 133 of the pilot valve 131 to the open position to thereby effect an opening operation of the circuit breaker in a manner to be hereinafter specifically described.

As the shaft structure 135 moves up, upon energization of the opening electromagnet 143, a latch part 201 of the latch 185 engages under a shoulder 203 formed on the shaft structure 135, so that when the solenoid 143 is deenergized, the shaft structure 135' will be latched in its upper or open position. The latch 185 is biased to this latching position by means of the spring 181, which operates to bias the shaft 177 downwardly, thereby biasing the bell-cnank type latch 185 in a counterclockwise direction about its pivot 189;

The circuit breaker 3 and all of the parts thereof, are shown in FIGS. 1-4 in the closed-circuit position. Re-

ferring to FIG. 2, fluid under pressure from the compressor 19 and accumulator 21 (FIG. 1), is Supplied to the upper side of the piston 33 through the conduit 65. Fluid under pressure is also supplied to the lower side of the piston 33 through the conduit 65, conduit 99, branch conduit 101, control valve port 124, control valve port 125, to the nozzle 105 of the main valve 73. The fluid then passes through the nozzle 105, orifice member 93, and the openings 83, 81 and 80 in the members 85, 79 and 69, respectively, into the cylinder 25 at the lower end of the piston 33. This high pressure fluid acting on the valve 117 maintains this valve in the closed circuit position shown in FIG. 2. Although the high pressure fluid is acting on both sides of the piston 33, there is a greater force on the lower side of the piston because of the difference in piston area, which diflerence is occasioned by the provision of the tube 37 and piston rod 39 at the upper side of the piston, so that the piston 33 is maintained in the closed-circuit position shown in FIG. 2.

As was previously described, the pilot valve member 133 of the pilot valve 131, is maintained in the closed circuit-position shown in FIGS. 14 by the spring 159 which biases the shaft structure 135 downward, overcoming the upward force exerted on the lower end of the valve member 133 by the high pressure fluid from the conduit 99.

When it is desired to open the circuit breaker 3, the opening solenoid 143 is momentarily energized, whereupon the armature 149, which is connected to the part 155" of the shaft structure 135, is attracted upward as seen in FIG. 3, overcoming the downward force resulting from the difference in forces between the spring member 159 and the fluid pressure through the conduit 99, to move the shaft structure 135 upward permitting upward movemerit of the valve member 133 under the bias of the fluid under pressure from the conduit 99. When the shaft structure 135 reaches its open position, it is latched by means of the latch 185 in the same manner previously described-L As the valve member 133 of the pilot valve 131 moves upward, fluid under pressure flows from the conduit 99, through a port 208 (FIG. 3), through a conduit 209 to the left Side of the piston 119 (FIG. 2) forcing the piston 119 arid valve 117 to the right as seen in FIG. 2.

As the valve 117 moves to the right, it closes off the right side of the port 125 blocking the passage of high pressure fluid and preventing the flow of this fluid into the main valve 73, thereby cutting off high pressure fluid from entering the lower end of the cylinder 25. At the same time, the movement to the right of the valve 117 opens the left side of the port 125 permitting the pressure of the control fluid that is exerted on the lower side of the valve 85 in the main valve 73 to be relieved through the nozzle 105, the left side of the port 125, a conduit 215'in the control valve 103, and a conduit 217 intothe sump 14. As the fluid pressure on the lower sideof the valve 85 and on the lower side of the piston 33'is relieved by movement to the right of the valve 117, the high pressure fluid on the upper side of the piston 33 forces the piston down moving the valve 85 down against the bias of the spring 87. This movement opens the port 108*permitting the fluid on the lower side" of the piston 33 to be'rap'idly dumpedthrough the openings 80 and 81 in the members 69 and 79, the port 108, the conduit 109 and into the sump chamber 14. As the piston 33 moves down, the piston rod 39, contact rod 5 and contacts 7 are moved to the open-circuit position. As the piston 33 6 reaches its lowermost position, the member 41 moves into the openings 80, 81 which act as a dashpot tocushion the stopping engagement of the piston 33 on the plate 69. When the piston 33 reaches its lowermost position relieving the downward fluid pressure on the check valve 89 and the valve member 85, the upward force of the spring 87 returns valve member to the position in which it is shown in FIG. 2.

When it is desired to close the circuit breaker 3, the

closing solenoid (FIG. 3) is momentarily energized moving the armature 17S and shaft 177 upward to rotate the latch clockwise about its pivot 189 to unlatch the latch part 201 from under the shoulder 203 of the shaft structure 135. The spring 159- thereupon acts to move the shaft structure 135 and valve member 133 down against the bias of the fluid pressure in the conduit 99 to close the port- 208 and prevent the passage of high pressure fluid through the conduit 209. This downward movement of the valve member 133 at the same time opens a port 219 permitting fluid to be dumped from the left side of the piston 119 (FIG. 2) through the conduit 209' (FIG. 3), port 219, a port 221, a conduit 223, and

the conduit 217 (FIG. 2) into the sump 14. As the pressure is relieved from the left side of the piston 119, the

fluid pressure from the branch conduit 101' acting on the valve 117, forces this valve back to the closed circuit position shown in FIG. 2.

When the valve 117 moves to its closed-circuit position, it closes the left side of the port 125 and opens the right side permitting the passage of high pressure fluid from the conduit 101, through the port'124, the port 125, the nozzle 105, the orifice member 93, the check valve port83,

and the openings 81 and 80, into the cylinder 25 on the is limited by engagement thereof with the cylindrical bumper 29.

From the foregoing description, it can be understood that the circuit breaker can be opened with increased speed because the sump is connected directly to a plate that serves as the endwall of the cylinder, so that the passage of fluid into this sump from the one side of the piston occurs only through a large main valve which is disposed within the sump chamber and which is also directly attached to the same end wall of the cylinder. The operating mechanism is made with a minimum amount of tubing providing a sturdy construction since all of the valve housings are fastened to each other to form a conipaet unit. An advantage of having less tubing is that the breaker requires less assembly time and there is less chance of a breakdown because of the fewer parts. The

breaker also .usesless hydraulic fluid pr'ovidingless friction and a minimum of masses that must be accelerated.

Thus, the improved breaker is more eflicient and faster in operation.

The beaker is controlled by three valves which are connected in series, and the forces acting on the pilot valve are such that the light-load latch, which is the only latch in the circuit breaker mechanism, need only hold a force strong enough to overcome a differencein opposing'forces that are acting on the pilot valve. With the provision of the light-load latch, the two solenoids which operate to effect opening and closing of the breaker need only be energized momentarily during the breaker operation.

The improved piston structure provides that the piston rod and the breaker operating rod need not necessarilybe perfectly aligned for effective operation.

Since numerous changes may be made in the above described construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. A circuit breaker comprising a stationary contact, a movable contact cooperable with said stationary contact and movable between two positions to open and close said contacts, hydraulic means operable to move said movable contact, said hydrauiic means comprising a piston housing having an opening therein, a piston disposed within said piston housing, means operatively connecting said piston with said movable contact, a valve member connected to said piston housing at said opening, a sump comprising a sump housing, said valve memher being disposed within said sump housing, and said valve member being operable to permit fluid to be dumped therethrough into said sump housing to effect movement of said piston to thereby effect movement of said movable contact from one to the other of said positions.

2. A circuit breaker comprising a stationary contact, a movable contact engaging said stationary contact and being movable away from said stationary contact to an open position, hydraulic means operable to move said movable contact, said hydraulic means comprising a piston housing having an opening therein, a piston disposed within said housing in a first position, means operatively connecting said piston with said movable contact, a valve member connected to said piston housing at said opening, a sump comprising a sump housing, said valve member being disposed within said sump housing, and said valve member being operable to permit fluid to be dumped therethrough into said sump housing to effect movement of said piston from said first position to a second position to thereby effect movement of said movable contact to said open position.

3. A circuit breaker comprising a stationary contact, a movable contact cooperable with said stationary contact and movable between two positions to open and close said contacts, hydraulic means operable to move said movable contact, said hydraulic means comprising a piston housing having an opening therein, a piston supported within said housing in a first position, means operatively connecting said piston with said movable contact, a valve member connected to said piston housing externally of said piston housing at said opening, a sump comprising a sump housing connected to said piston housing externally of said piston housing, said valve member being disposed within said sump housing, and said valve member being operable to permit fluid to be dumped therethrough into said sump housing to effect movement of said piston from said first position to a second position to thereby move said movable contact iirom a closed position to an open position.

4. A circuit breaker comprising a stationary contact, a movable contact in engagement with said stationary contact and movable to an open position out of engagement with said stationary contact, hydraulic means operable to move said movable contact, said hydraulic means comprising a piston housing having an opening therein, a piston supported within said piston housing in a first position, means operatively connecting said piston with said movable contact, a valve member connected to said piston housing externally of said piston housing at said opening, a sump comprising a sump housing connected to said piston housing, said valve member being disposed within said sump housing, a control valve connected to said sump housing externally of said sump housing and operable to control operation of said valve member, and means for operating said control valve to thereby operate said valve member to permit fluid to be dumped through said valve member into said sump housing to effect movement of said piston from said first position to a second position to thereby move said movable contact to said open position.

5. A circuit breaker comprising, in combination, a stationary contact, a movable contact cooperable with the stationary contact to open and close the breaker, hydraulic means operable to effect movement of the movable contact, the hydraulic means comprising, a cylinder, a plate at one end of the cylinder, a sump connected to the plate, a main valve disposed within the sump and connected to the plate, a control valve connected to the sump and operable to control operation of the main valve, the control valve also being connected to the main valve, a pilot valve being connected to the control valve, said pilot valve being operable to control operation of the control valve, and means for operating the pilot valve.

6. A circuit breaker comprising, in combination, a stationary contact, a movable contact cooperable with the stationary contact to open and close the breaker, a cylinder, a piston movable within the cylinder to move the movable contact, a main valve operable to effect operation of the piston, a control valve operable to operate the main valve, a pilot valve operable to operate the control valve, and the pilot valve being movable to a first position to effect closing of the breaker and being movable to a second position to effect opening of the breaker.

7. A circuit breaker comprising, in combination, a stationary contact, a movable contact cooperable with the stationary contact to open and close the breaker, a cylinder, a piston movable within the cylinder to move the movable contact, a main valve operable to effect operation of the piston, a control valve operable to operate the main valve, a pilot valve operable to operate the control valve, the pilot valve being movable to a first position to effect closing of the breaker and to a second position to effect opening of the breaker, and light-load latching means for latching the pilot valve in the second position.

8. A circuit breaker comprising, in combination, a stationary contact, a movable contact cooperable with the stationary contact to open and close the breaker, a cylinder, a piston movable within the cylinder to move the movable contact, a main valve operable to effect operation of the piston, a control valve operable to operate the main valve, a pilot valve operable to operate the control valve, said pilot valve comprising a valve member movable to a first position to effect closing of the breaker and being movable to a second position to effect opening of the breaker, fluid pressure means biasing said valve member toward its open-circuit position, spring means biasing said valve member toward its closed-circuit position, the force of said spring means overcoming the force of said fluid pressure means to normally hold said valve member in its closed circuit position, means for relieving the force of said spring means on said valve member to permit opening of said circuit breaker, and latching means for maintaining said relief of force of said spring means on said valve member.

9. A circuit breaker comprising, in combination, a stationary contact, a movable contact cooperable with the stationary contact to open and close the breaker, a cylinder, a piston movable Within the cylinder to move the movable contact, a main valve operable to effect operation of the piston, a control valve operable to operate the main valve, a pilot valve operable to operate the control valve, the pilot valve being movable between two operating positions to effect opening and closing of the breaker, electromagnetic means operable to move the pilot valve and comprising a first electromagnet and a second electromagnet, the first electromagnet when momentarily energizcd effecting movement of the pilot valve to one of said positions, the second electromagnet when momentarily energized eitecting movement of the pilot valve to the other of said positions, and latching means operable to maintain the pilot valve in said other of said positions.

10. A circuit breaker comprising, in combination, a stationary contact, a movable contact movable to open and close the breaker, a cylinder, a piston reciprocable in the cylinder, a piston rod connected to the piston by means of a connection that permits a swivelling motion of the piston rod relative to the piston, means operatively connecting said piston rod with said movable contact, and means for reciprocating said piston to reciprocate said piston rod to effect opening and closing of the contacts.

11. A circuit breaker comprising, in combination, a stationary contact, a movable contact cooperable with the stationary contact to open and close the breaker, a cylinder having an end wall, a piston movable within the cylinder, an elongated piston rod extending through an opening in the end wall, attaching means attaching said piston rod to said piston, said piston rod moving longitudinally with said piston movement to efiect opening and closing movements of the movable contact, said attaching means of said piston rod comprising means permitting said piston rod to swivel about its longitudinal axis relative to said piston, and means sealing said end wall opening.

12. A circuit breaker comprising a stationary contact and a movable contact movable to open and close said contacts, a cylinder, means reciprocal to move said movable contact to open and close said contacts, said reciprocal means comprising a piston reciprocal in said cylinder, a tubular seal member connected to the piston and protruding from the cylinder at least during part of the piston stroke, a piston rod within the tubular seal member and connected to the piston by means of a ball-andsocket type connection, and means operatively connecting said piston rod with said movable contact.

13. A circuit breaker comprising a stationary contact, a movable contact, a cylinder having an end wall, means reciprocal to move said movable contact into and out of engagement with said stationary contact, said reciprocal means comprising a piston reciprocal within the cylinder, means for etfecting reciprocation of the piston, a tubular member connected to the piston and extending through an opening in said end wall at least during part of said piston movement, a piston rod disposed within said tubular member, a ball-and-socket type connecting means connecting said piston rod to said piston, said piston rod extending through said opening in said end wall, and sealing means in said end wall opening slidably receiving said tubular member.

References Cited in the file of this patent UNITED STATES PATENTS 2,486,787 Johnson Nov. 1, 1949 2,700,488 Rafierty Ian. 25, 1955 2,730,589 Perry et al Jan. 10, 1956 2,765,378 Perry et al Oct. 2, 1956 2,987,311 Schilling et al June 6, 1961 2,995,148 Novak et a1 Aug. 8, 1961 

1. A CIRCUIT BREAKER COMPRISING A STATIONARY CONTACT, A MOVABLE CONTACT COOPERABLY WITH SAID STATIONARY CONTACT AND MOVABLE BETWEEN TWO POSITIONS TO OPEN AND CLOSE SAID CONTACTS, HYDRAULIC MEANS OPERABLE TO MOVE SAID MOVABLE CONTACT, SAID HYDRAULIC MEANS COMPRISING A PISTON HOUSING HAVING AN OPENING THEREIN, A PISTON DISPOSED WITHIN SAID PISTON HOUSING, MEANS OPERATIVELY CONNECTING SAID PISTON WITH SAID MOVABLE CONTACT, A VALVE MEMBER CONNECTED TO SAID PISTON HOUSING AT SAID OPENING, A SUMP COMPRISING A SUMP HOUSING, SAID VALVE MEMBER BEING DISPOSED WITHIN SAID SUMP HOUSING, AND SAID VALVE MEMBER BEING OPERABLE TO PERMIT FLUID TO BE DUMPED THERETHROUGH INTO SAID SUMP HOUSING TO EFFECT MOVEMENT OF SAID PISTON TO THEREBY EFFECT MOVEMENT OF SAID MOVABLE CONTACT FROM ONE TO THE OTHER OF SAID POSITIONS. 